Confinement ring drive

ABSTRACT

A confinement assembly for a semiconductor processing chamber is provided. The confinement assembly includes a plurality of confinement rings disposed over each other. Each of the plurality of confinement rings are separated by a space and each of the plurality of confinement rings have a plurality of holes defined therein. A plunger extending through aligned holes of corresponding confinement rings is provided. The plunger is moveable in a plane substantially orthogonal to the confinement rings. A proportional adjustment support is affixed to the plunger. The proportional adjustment support is configured to support the confinement rings, such that as the plunger moves in the plane, the space separating each of the plurality of confinement rings is proportionally adjusted. In one embodiment the proportional adjustment support is a bellows sleeve. A semiconductor processing chamber and a method for confining a plasma in an etch chamber having a plurality of confinement rings are provided.

CLAIM OF PRIORITY

This application is a divisional application based on U.S. patentapplication Ser. No. 11/044,576 filed Jan. 27, 2005 now U.S. Pat. No.7,364,623 which is herein incorporated by reference in its entirety forall purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to semiconductor manufacturingand, more particularly, to a method and apparatus for providing aconfinement ring drive that provides proportional spacing between theconfinement rings over a travel range.

2. Description of the Related Art

During the manufacturing of semiconductor-based devices, it is common todeposit layers of material onto a substrate. Each of the layers ofmaterial may undergo an etching process. Etching of the layers may beaccomplished by a wide variety of techniques including plasma-enhancedetching.

The plasma etchers performing these operations may include confinementrings to confine the plasma within a region of the etch chamber. Theconfinement rings serve to confine the plasma and also protect thechamber walls. However, the current systems are not well suited toadjust to changes within the etch chamber during the processingoperation. In particular, the current systems cannot maintain equal gapsbetween the confinement rings because of restrictions in the confinementring drive system. The lack of capability to proportionally adjust theconfinement rings may result in a change of the gas flow dynamics, alack of reproducibility between successive etch operations, e.g., in anetch rate, or the plasma going unconfined, which results in the chamberwalls being attacked by the plasma.

In view of the foregoing, there is a need for a method and apparatusthat provides for uniform movement of the confinement rings over a rangeof travel of the confinement rings.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention fills these needs by providing amethod and apparatus for proportionally maintaining spacing betweenconfinement rings. It should be appreciated that the present inventioncan be implemented in numerous ways, including as a method, a system, oran apparatus. Several inventive embodiments of the present invention aredescribed below.

In one embodiment, a confinement assembly for a semiconductor processingchamber is provided. The confinement assembly includes a plurality ofconfinement rings disposed over each other. Each of the plurality ofconfinement rings are separated by a space and each of the plurality ofconfinement rings have a plurality of holes defined therein. A plungerextending through aligned holes of corresponding confinement rings isprovided. The plunger is moveable in a plane substantially orthogonal tothe confinement rings. A proportional adjustment support is affixed tothe plunger. The proportional adjustment support is configured tosupport the confinement rings, such that as the plunger moves in theplane, the space separating each of the plurality of confinement ringsis proportionally adjusted. In one embodiment the proportionaladjustment support is a bellows sleeve.

In another embodiment, a semiconductor processing chamber is provided.The semiconductor processing chamber includes a plurality of confinementrings configured to confine a plasma within a region of the chamber. Aplurality of bellows sleeves supporting the confinement rings is alsoincluded. A plurality of plungers affixed to corresponding bellowssleeves is included. The plurality of plungers move along an axissubstantially orthogonal to a plane of the confinement rings such thatmovement of the plurality of plungers results in spaces between each ofthe plurality of confinement rings to proportionally adjust.

In yet another embodiment, a method for confining a plasma in an etchchamber having a plurality of confinement rings is provided. The methodinitiates with performing an etch process in the etch chamber. Then, theprocessing parameters of the etch chamber are monitored. Next, spacingbetween each of the plurality of the confinement rings is adjusted in amanner that the spacing adjustment applied to each of the plurality ofthe confinement rings is substantially equal.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, andlike reference numerals designate like structural elements.

FIG. 1 is a simplified cross-sectional schematic diagram illustrating anexemplary plasma etching chamber, in accordance with one embodiment ofthe present invention.

FIG. 2 illustrates, in accordance with one embodiment of the presentinvention, a cross-sectional schematic diagram of a plunger arrangementof a cam-based arrangement for proportionally moving confinement rings.

FIG. 3 shows a simplified schematic diagram of the top view of thecam-based arrangement in accordance with one embodiment of the presentinvention.

FIG. 4 is an expanded schematic diagram of the plunger and bellowssleeve that is capable of uniformly adjusting the spacing between theconfinement rings in accordance with one embodiment of the invention.

FIG. 5 is a simplified schematic diagram of a hinged lever assembly foruniformly adjusting the spacing between confinement rings as analternative embodiment to the bellows sleeve of FIG. 4.

FIG. 6 is a simplified schematic diagram of one of the hinged levers ofthe hinged lever assembly of FIG. 5.

FIG. 7 is a flowchart diagram of the method operations for confining aplasma in an etch chamber having a plurality of confinement rings inaccordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An invention is described for a system, apparatus and method forproportionally adjusting confinement rings to enhance etch operationswithin a semiconductor processing chamber. It will be obvious, however,to one skilled in the art, that the present invention may be practicedwithout some or all of these specific details. In other instances, wellknown process operations have not been described in detail in order notto unnecessarily obscure the present invention.

The embodiments of the present invention provide a system, apparatus,and method for providing substantially linear control of the movement ofthe confinement rings over the entire range of travel of a plunger. Thisresults in uniform movement of the confinement rings so that the spacingbetween each confinement ring remains substantially the same relative toone another. That is, the embodiments described herein allow forproportional control of the spacing between the confinement rings. Inone embodiment, a confinement ring drive capable of providing uniformspacing control for a plurality of confinement rings through a bellowssleeve is provided. The confinement ring drive incorporates a cam-basedarrangement that drives a plunger which results in the uniform movementof the confinement rings, as discussed in more detail below.

FIG. 1 is a simplified cross-sectional schematic diagram illustrating anexemplary plasma etching chamber, in accordance with one embodiment ofthe present invention. Within plasma etching chamber 101, electrode 109is disposed over a volume within which plasma 111 is to be generated.Wafer support structure 105 is located below the volume in which plasma111 is to be generated. In one embodiment, wafer support structure 105is an electrostatic chuck. Wafer support structure 105 is defined tosupport wafer 107 during exposure to plasma 111.

Plasma etching chamber 101 of FIG. 1 also includes a set of confinementrings 320 a-d disposed around a periphery of the volume within whichplasma 111 is to be generated. Confinement ring controller 121 isprovided to control movement of the set of confinement rings 320 a-d. Inone embodiment, confinement ring controller 121 is represented assoftware executing on a computer system. In another embodiment,confinement ring controller 121 is represented as hardware (e.g.,circuitry implemented on a chip). Regardless of the particularembodiment, confinement ring controller 121 is capable of interfacingwith mechanics configured to move the set of confinement rings 320 a-din accordance with instructions received from confinement ringcontroller 121. Confinement ring controller 121 is also capable ofsetting programmable periods of time for moving and/or holding the setof confinement rings 320 a-d.

Still referring to FIG. 1, window 115 is provided in wall 103 of plasmaetching chamber 101 for viewing optical emissions, or other suitableprocess indicators, produced within the volume to be occupied by plasma111. Transmission device 117 is provided for transmitting opticalemissions, or other suitable process indicator transmissions gatheredthrough window 115 to process monitoring equipment 119 for analysis. Inone embodiment, the transmission device 117 is a fiber optic cable.However, it should be appreciated that the transmission device 117 canbe any other component capable of adequately transmitting data. Processmonitoring equipment 119 represents one or more components or system ofcomponents capable of separating the captured input, e.g., an opticalinput into distinct channels (i.e., wavelengths) for analysis. In oneembodiment, window 115 incorporates a pressure transducer to monitor thepressure within chamber 101. The pressure value, or a signal triggeredby the pressure value captured through process monitoring equipment 119,is communicated to confinement ring controller 121. In turn, plungers310 are driven in an orthogonal direction relative to confinement rings320 a-d. In one embodiment, rotation of cam ring 304 causes plungers 310to move. It should be appreciated that the pressure within the chambermay be monitored through any known means. The monitored pressure is thencommunicated to confinement ring controller 121 in order to determinewhether to adjust the confinement ring spacing.

During operation of chamber 100 of FIG. 1, the set of confinement rings320 a-d serve to confine plasma 111 to a particular volume (“plasmaconfinement volume”) and control a pressure within the plasmaconfinement volume. The set of confinement rings 320 a-d can be moveduniformly to proportionally increase and decrease a spacing or gapbetween adjacent confinement rings. In one embodiment, the set ofconfinement rings 320 a-d are moved through use of a cam ring. However,it should be appreciated that many other manipulation devices can beused to move the set of confinement rings 320 a-d in accordance withetching process requirements. Movement of the set of confinement rings320 a-d can be defined to cause the gaps between adjacent confinementrings to uniformly change. As will be illustrated below, the movement ofplungers 310 causes confinement rings 320 a-d to move proportional toeach other to uniformly widen or close a gap between the confinementrings.

It should be appreciated that pressure control within the plasmaconfinement volume is necessary during operation due to thermalvariations within the plasma etching chamber 101. Temperatures withinthe chamber may change during operation due to process conditions. Forexample, etching by-product deposition may occur on the chamber internalsurfaces during operation. The etching by-product deposition will affectthe heat transfer characteristics of the chamber, thereby causingtemperature variations within chamber 101. The temperature variationswithin chamber 101 will have a corresponding affect on the pressurewithin the chamber. As discussed in more detail below, during etchingprocesses that require a substantially constant pressure, a confinementring drive is provided for controlling the pressure within the chamber.

In chamber 101, processing gases flow through the gaps between adjacentconfinement rings to exit the plasma confinement volume. Thus, movementof the set of confinement rings serves to adjust a flow area providedfor processing gas egress from the plasma confinement volume. Therefore,adjustment of the subject flow area provides a corresponding control ofthe pressure within the plasma confinement volume. During the etchingprocess, the set of confinement rings 320 a-d are uniformly moved, asdescribed in more detail below, to maintain a target pressure within theplasma confinement volume during the processing.

In accordance with one aspect of the present invention, there isprovided a cam-based arrangement for uniformly raising and loweringconfinement rings 320 a-d within plasma processing chamber 101. Thecam-based arrangement utilizes cam followers and cam ring 304 to raiseand lower plungers 310, which are connected to the confinement rings. Ascam ring 304 rotates, plungers 310 are raised or lowered in anorchestrated manner to raise or lower confinement rings 320 a-d.

In accordance with another aspect of the present invention, the camregions of the cam ring may be profiled to achieve fine control ofconfinement ring movement in order to fine-tune the pressure drop acrossthe confinement ring area. By moving only the confinement rings tocontrol the pressure drop across the confinement ring area (whichaffects the pressure at the substrate surface), the pressure at thesubstrate surface may be controlled without significantly affectingother etch parameters.

FIG. 2 illustrates, in accordance with one embodiment of the presentinvention, a cross-sectional schematic diagram of a plunger arrangementof a cam-based arrangement for proportionally moving confinement rings.Plunger arrangement 300 includes wheel 302, which is shown to be inrolling contact with cam ring 304. Wheel 302 is adjustably mounted onbacking plate 306 (via, for example, a bolt and slot arrangement).Backing plate 306 may be mounted on the reactor top and is essentiallyimmobile with respect to the reactor top.

Cam follower 308 is mounted on plunger 310. Plunger 310 and attached camfollower 308 are urged toward a lower surface 312 of cam ring 304 byspring 314. Cam follower 308 stays in rolling contact with lower surface312 to permit plunger 310 to rise or fall with the contours in lowersurface 312. Spring 314 always urges plunger 310 and cam follower 308toward lower surface 312 of cam ring 304. As shown, plunger 310 movesupward and downward parallel to axis 380, which is substantiallyorthogonal to the plane defined by the confinement rings 320 a-c.

Still referring to FIG. 2, bellows sleeve 500 is disposed over plunger310 and affixed thereto. Bellows sleeve 500 includes a number ofprotrusions, which act to support confinement rings 320 a-c. As plunger310 is raised or lowered, confinement rings 320 a-c are correspondinglyraised or lowered in a uniform manner. It should be appreciated that theprotrusions of bellows sleeve 500 will fold and expand similar to anaccordion and cause confinement rings 320 a-c to be uniformly spreadapart or brought closer together. A pair of seals 360 mounted in groovesformed in the chamber top permit the pressure within the plasmaprocessing chamber to be maintained as plunger 310 moves up and downfollowing the contour in lower surface 312 of cam ring 304. It should beappreciated that although two seals are shown, any number of seals maybe employed as desired. Additionally, any suitable number of confinementrings may be used within the processing chamber.

As mentioned earlier, the up and down movement of plunger 310 iscontrolled by the contour in lower surface 312 of cam ring 304. As shownin FIG. 2, lower surface 312 includes a cam region 362, of which thereis preferably one for every plunger assembly. Cam region 362 preferablyincludes an inclining surface 366, which causes plunger 310 to be movedupward as cam ring 304 is rotated in the direction of arrow 368, and adeclining surface 370, which causes plunger 310 to be moved downward ascam ring 304 is rotated in the direction of arrow 390. In oneembodiment, declining surface 370 is not employed for controllingplunger 310. Instead, plunger 310 is moved upward and downward employingonly inclining surface 366 as the cam ring is rotated back and forth andcam follower 308 follows the contour of inclining surface 366.

Inclining surface 366 of FIG. 2 may include two separate regions havingtwo different slopes. As illustrated slope 374 of inclining surface 366is steeper than a slope 372 to allow plunger 310 to move upward anddownward a greater distance per degree of rotation of cam ring 304.Slope 374 may be used for coarse control, e.g., during wafer transport,and slope 372 may be employed for fine control of the position of theconfinement rings, e.g., during pressure control. It should beappreciated that the use of bellows sleeve 500 provides for theproportional adjustment of the gaps between confinement rings 320 a-c.In addition, the gap between insulator 150 and the top confinement ringand the gap between surface 108 and the bottom confinement ring may beadjusted. Further information on the cam drive assembly may be found inU.S. Pat. No. 6,019,060, which is hereby incorporated by reference inits entirety for all purposes.

FIG. 3 shows a simplified schematic diagram of the top view of thecam-based arrangement in accordance with one embodiment of the presentinvention, including a motor 402 that is employed to rotate cam ring304. Motor 402 is coupled to cam ring 304 via a belt 404. Belt 404 isattached to cam ring 304 at points 406 and 408 although it may bepermitted to wrap around cam ring 304 if desired. A tensioningarrangement 410 takes up the slack in belt 404 and pulls cam ring 304toward motor 402 to urge the inner surface of cam ring 404 to be inrolling contact with rollers 412 and 414 (of which two are necessary todefine the center of rotation of the cam ring although any additionalnumber of rollers may be provided).

Three plunger assemblies 416 are shown disposed about a cam ring in FIG.3. However, any number of plunger assemblies may be employed with thecam ring. As can be appreciated by those skilled in the art, theplungers in assemblies 416 move in an orchestrated manner as theirattached cam followers ride on the lower surface of the cam ring, and ascam ring is rotated clockwise and counterclockwise by motor 402 (viabelt 404). Optional positional feedback arrangement 420, which may beimplemented in the form of a linear potentiometer, is coupled to belt404. However, any other type of positional sensor arrangement may beemployed to provide data pertaining to the rotation of the cam ring.From the feedback data and the known profiles of the cam regions in thecam ring, the position of plungers 310 and the confinement rings in theplasma processing chamber may be derived.

In accordance with another aspect of the present invention, the abilityof the cam-based arrangement to uniformly raise or lower the confinementrings without affecting the chamber volume enables the embodimentsdescribed herein to achieve pressure control during etching. Althoughthe etch pressure (i.e., the pressure at the substrate's surface duringetching) can be changed by many mechanisms (e.g., changing the inputrate of the etchant source gas), the response would be improved ifpressure control is accomplished locally (i.e., in the vicinity of thesubstrate).

FIG. 4 is an expanded schematic diagram of the plunger and bellowssleeve that is capable of uniformly adjusting the spacing between theconfinement rings in accordance with one embodiment of the invention.Bellows sleeve 500 is disposed over plunger 310. Fastener 318, which inone embodiment is a plastic bolt, anchors bellows sleeve 500 to a bottomsurface of plunger 310. It should be appreciated that bellows sleeve 500may also be affixed to a top portion of plunger 310. By contracting orexpanding the spacing between protrusions of bellows sleeve 500, throughthe movement of plunger 310, the spacing between correspondingconfinement rings will change. That is, the distances represented byarrows A and B will change in a uniform manner, i.e., proportional,relative to one another. Additionally, plunger 310 may be positionedwithin the chamber so that the top and bottom confinement rings aredefined at a certain distance from a top surface and a bottom surface,respectively, of the chamber. It should be appreciated that by evenlyspacing each of the confinement rings avoids a largest space between theconfinement rings from dominating how well the plasma remains confined.In one embodiment, the surface of bellows sleeve 500 has a coatingapplied thereto, such as a TEFLON™ coating. It should be appreciatedthat the coating may be any suitable coating that is compatible with theplasma environment and does not shed particles that would contaminatethe substrate being etched. In addition, the coating is pliable in orderto accommodate the contraction and expansion of bellows sleeve 500.

FIG. 5 is a simplified schematic diagram of a hinged lever assembly asan alternative embodiment to the bellows sleeve of FIG. 4. Hinged leverassembly 503 includes a plurality of hinged levers 504 pivotablyinterconnected through pivot points 502. Plunger 310 is affixed tocrosspiece 501. Thus, the movement of plunger 310 forces confinementrings 320 a-c to move proportional to one another so that the spacingbetween the confinement rings remains relatively consistent. Morespecifically, as plunger 310 is moved down towards confinement rings 320a-c, the spacing between the confinement rings becomes uniformlysmaller. As plunger 310 is moved in an upward direction away fromconfinement rings 320 a-c, the spacing between the confinement ringsbecomes uniformly larger.

FIG. 6 is a simplified schematic of one of the hinged levers of thehinged lever assembly of FIG. 5. Hinged lever 504 includes a pluralityof pivot points 502. Pivot points 502 are holes defined through lever504 in one embodiment. In another embodiment, corners 508 and 510 oflever 504 are rounded. In addition, surface 512, on which theconfinement ring rests may be angled to better accommodate theconfinement rings over the travel range and compensate for any tilting.In FIG. 6, hinged lever 504 is shown with a slight indentation to thesupport portion having surface 512. In one embodiment hinged lever 504may be composed of a metal such as stainless steel. In anotherembodiment, the metal may be coated with a compatible coating asmentioned above with reference to the bellows sleeve coating. Hereagain, the metal and coating may be of any material compatible with theetching application and environment.

FIG. 7 is a flowchart diagram of the method operations for confining aplasma in an etch chamber having a plurality of confinement rings inaccordance with one embodiment of the invention. The method initiateswith operation 520 where an etch process is performed in an etchchamber. Here, any suitable etch process may be performed that requiresa plasma to be confined and generated. The method advances to operation522 where the processing parameters of the etch chamber are monitored.For example, the pressure within the chamber may be monitored throughknown techniques. As the etch operation progresses the temperaturechange and other factors may cause the pressure to change. One techniqueto counteract the pressure change is to adjust the spacing between theconfinement rings according to the embodiments described herein. Inoperation 524 the spacing between the confinement rings is adjusted sothat the spacing adjustment between each confinement ring issubstantially equal. As described above with reference to FIGS. 2-6, theuse of a bellows sleeve or a hinged lever assembly, in conjunction withthe cam drive, will guarantee the proportional movement of eachconfinement ring. By maintaining proportionally consistent spacingbetween the confinement rings, enhanced control of the etch operation,as well as preventing one large space from dominating how well theplasma remains confined are achieved.

In summary, the above-described embodiments provide a method andapparatus for enhanced control of inter-confinement ring spacing.Through the drive system described above, substantially equal spacingbetween the confinement rings is achieved by proportionally varying theconfinement ring spacing over a wide range of set points. The bellowssleeve or the hinged lever assembly act as a proportional adjustmentsupport that translates movement from the plunger into proportionalmovement for each of the confinement rings.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims. In the claims,elements and/or steps do not imply any particular order of operation,unless explicitly stated in the claims.

1. A method for confining a plasma in an etch chamber having a pluralityof confinement rings, each of the plurality of confinement ringssupported by a plurality of bellows sleeves, comprising methodoperations of: performing an etch process in the etch chamber;monitoring processing parameters of the etch chamber; and adjustingspacing between each of the plurality of the confinement rings in amanner that the spacing adjustment applied to each of the plurality ofthe confinement rings is substantially equal, the adjusting including,moving a plurality of plungers along an axis substantially orthogonal toa plane of the plurality of confinement rings such that movement of theplurality of plungers results in spaces between each of the plurality ofconfinement rings to proportionally adjust, wherein each of theplurality of bellows sleeves includes a number of protrusions, theprotrusions having a diameter greater than a diameter of a hole definedthrough each of the plurality of confinement rings, and wherein one ofthe plungers and one of the bellows sleeves is disposed through thehole.
 2. The method of claim 1, wherein the method operation ofmonitoring processing parameters of the etch chamber includes,monitoring a chamber pressure; determining whether the chamber pressureis to be increased or decreased.
 3. The method of claim 1, wherein themethod operation of adjusting spacing between each of the plurality ofthe confinement rings includes, expanding a set of bellows to decrease apressure of the chamber; and contracting the set of bellows to increasethe pressure of the chamber.
 4. The method of claim 1, wherein methodoperation of causing a plunger to move in a direction substantiallyorthogonal to the plurality of confinement rings includes, changing aposition of a cam follower affixed to the plurality of plungers.
 5. Themethod of claim 1, wherein the adjusting the spacing is triggered by achange of one of the processing parameters.